Phenomenological Studies and Analysis Techniques to Search for Light Dark Matter With NEWS-G

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The NEWS-G collaboration uses gas-filled Spherical Proportional Counters (SPCs) to search for low-mass dark matter. As one of several competing collaborations pushing the low-energy frontier of particle detection technology, NEWS-G now is preparing for an exciting new experiment at SNOLAB. In addition to an upgraded detector, an improved understanding of SPCs, and sophisticated analysis techniques are needed to continue the search for dark matter. This thesis presents work done to address several of the outstanding challenges that NEWS-G must face. The possibility of measuring the ionization quenching factor of gases with a neutron capture experiment is explored, but ultimately ruled-out. A likelihood analysis framework is implemented for NEWS-G, and validated through a case-study of the neutrino floor. Finally, the COM-Poisson distribution is proposed as a novel tool to model ionization statistics at the single electron-regime, and to assess the impact that the Fano factor may have on direct detection experiments.